The present invention relates to a heat treatment apparatus and a substrate processing system incorporated in a resist coating/developing system for heating or cooling a substrate such as a semiconductor wafer or an LCD (liquid crystal display) substrate.
In a photolithography process for manufacturing a semiconductor device, a photoresist is coated on the substrate and the resist-coated film is exposed to light and developed. The series of processes is carried out in the resist coating/developing system constituted of heating units such as a prebake unit and a post bake unit. Each of these heating units has a hot plate having a built-in heater of a resistance heating type. In the peripheral portion of the hot plate, a plurality of small projections are provided. The substrate is supported by these small projections, so that a small space is created between the substrate and the hot plate. The substrate is heated by receipt of heat radiation (heat energy beams) emitted from the hot plate.
At this time, air around the hot plate is heated and raised in temperature. The hot air thus heated rises up within a chamber and exhausted through an exhaust port formed through an upper cover. The hot air comes into an ascending air stream which flows from the outer peripheral portion of the hot plate toward the center and is converged and exhausted from a position right above the substrate. As a result, part of particles contained in the air may fall down on the substrate, causing a problem of particle adhesion.
In addition a conical-form recess is formed around the exhaust port in the lower surface portion of the cover. The hot air is guided along the conical-form recess, formed into a spiral air stream and flows toward the exhaust port. However, the flow of the hot air tends to stagnate near right below the exhaust port.
The stagnant hot air has a thermal influence upon the wafer W, rendering temperature of the wafer W non-uniform.
Furthermore, the height from the floor to the ceiling of the clean room is limited to a certain range. Therefore, it is necessary to reduce the height of the apparatus. However, a conventionally-used heat treatment apparatus has the upper cover, so that the height of the apparatus is large.